JPH0316024A - Production of magnetic disk - Google Patents

Abstract

PURPOSE:To improve magnetic characteristics such as coercive force, squareness ratio and coercive force squareness ratio in the circumferential direction by providing Ni-P plating on an aluminum alloy substrate, forming concentrical lines by a texturing method, and then forming a magnetic recording layer thereon. CONSTITUTION:A disk substrate, 5.25 inch in diameter, of aluminum alloy is coated with Ni-P plating film, polished for finish, and subjected to electroless Ni-P plating to form 10 - 100nm thick film. Then the substrate is treated by texturing to form concentrical lines of 100 - 600Angstrom roughness height Rtm. Then the substrate is washed with pure water to remove abrasives deposited on the surface, dried by use of a spin dryer and then stored. After stored, the substrate is coated with a Co-P magnetic plating film by conventional electroless plating method. Further, a protective film and a lubricating film are formed thereon. Thereby, the obtd. medium is improved in magnetic characteristics such as coercive force, squareness ratio and coercive force squareness ratio in the circumferential direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a magnetic disk, and in particular to a method for manufacturing a plated magnetic disk whose electromagnetic conversion characteristics are improved by increasing magnetic anisotropy.

[Conventional technology]

In recent years, as the density of magnetic recording devices has increased, the form of magnetic disks has been replaced from coated types to types with thin film media formed by plating or sputtering. As the density of magnetic recording devices continues to increase, demands for increasing the magnetic anisotropy of magnetic recording media are also increasing.

For this reason, for example, in plated magnetic disks that use plating to form thin film media, the surface of the plated layer is polished to create concentric streaks called texturing, and then the surface of the plated layer is polished. Measures have been taken to increase magnetic anisotropy by modifying the shape of the magnetic plating layer. [Problems to be solved by the invention] However, sufficient magnetic anisotropy cannot be obtained only by using a textured substrate;
Immediately after texturing, the magnetic media is plated.
However, there was a problem in that magnetic performance deteriorated and fluctuated. Therefore, an object of the present invention is to provide a method for manufacturing a magnetic disk that can increase the magnetic anisotropy of a magnetic recording medium and stably improve the T4 magnetic conversion characteristics.

[Means to solve the problem]

A method for manufacturing a magnetic disk according to the present invention to achieve the above object uses an aluminum alloy disk or an aluminum alloy disk having a Ni-P plated surface as a base, and polishes the base surface smooth to coat the Ni-P plated surface. The gist of the structure is to apply P plating, then to form streaks in the circumferential direction by texturing, and then to form a magnetic recording layer. In the above structure, the effect of imparting magnetic anisotropy can be maintained for a long period of time by adding a step of drying or storing the substrate after texturing under an inert gas atmosphere. Argon, nitrogen, etc. are effectively used as inert gases. The flow sheet of the preferred manufacturing process of the present invention is shown in FIG. 1, and in contrast to the manufacturing process flow sheet of the conventional technology shown in FIG. It is also characterized by the addition of the above-mentioned drying or storage process under an inert gas atmosphere as a post-texturing process. [Function] According to the manufacturing process of the present invention, coercive force in the circumferential direction, squareness ratio,
Magnetic properties such as coercive force squareness ratio are improved. Further, the magnetic properties do not vary depending on the thickness of the Ni--P plating layer before texturing, the roughness of the substrate surface during texturing, etc., and stable performance is always provided.

Furthermore, by performing a drying or storage process under an inert gas atmosphere after texturing, it is possible to maintain magnetic anisotropy for a long period of time. [Example] Hereinafter, the present invention will be specifically described based on Examples.

(1> Manufacture of magnetic disks A 5.25-inch diameter base plated with Nj-P on the surface of an aluminum alloy disc was used, and the surface was polished. Commercially available electroless Ni-P A plating layer with a thickness of 10 to 100 nm was formed using a plating solution.

Next, a texturing process was performed to create striations with a surface roughness Rtm of 100 to 600 in the concentric direction.
The abrasive grains used for texturing processing may be either organic abrasive grains or fixed abrasive grains. After texturing, some adhering abrasive grains were removed by washing in pure water. This cleaning is performed using scrub cleaning or high-pressure water cleaning. Next, the cleaned substrate was dried with a spin dryer and stored, and as another example, stored in an argon gas atmosphere.

Co is applied to the substrate surface after storage using normal electroless plating means.
A magnetic plating layer made of -P was formed, and a protective film and a lubricating film were further formed using conventional methods. (2) Evaluation of characteristics In order to evaluate the magnetic characteristics of the magnetic disk according to the present invention obtained in this way, a vibrating sample magnetometer (VMS) was used.
The magnetic hysteresis curve was measured when a maximum magnetic field of 5 KOe was applied using the . The typical results are shown in Figure 3.

As a comparative example, FIG. 4 shows a hysteresis curve of a conventional magnetic disk in which the Ni--P plating layer was subjected to texturing.

Further, Table 1 shows a comparison of the magnetic properties measured for Examples and Comparative Examples.

Table 1 From the results shown in Figures 3 and 4 and Table 1, it can be seen that the magnetic disk manufactured by the present invention has magnetic properties such as coercive force in the circumferential direction, squareness ratio, coercive force squareness ratio, etc. compared to the conventional magnetic disk. It turns out that the characteristics are improved. These magnetic properties did not change even if the film thickness was changed by Ni-P plating before texturing, and they were not affected by changes in the substrate roughness caused by texturing. ．． Figure 5 compares and contrasts the changes in magnetic properties of magnetic properties over time after texturing for examples of the present invention (dry storage and argon gas storage) and examples stored in ultrapure water. In dry storage and storage in argon gas, stable coercive force was maintained even after 200 hours of long-term storage, but in the case of underwater storage, a decrease in magnetic properties was observed after about 4 hours. Note that using non-oxidizing nitrogen gas instead of argon gas also had a long-term stabilizing effect on magnetic properties, and it was possible to change the storage time by controlling the purity of the gas. Table 2 shows the results of measuring the electromagnetic conversion characteristics of each magnetic disk according to Examples and Comparative Examples using a commercially available single plate tester.

Table 2 Head used: yl film type Flying height: 0.20I! m Track width: 11. O* Gap length: 0.8, n From the results in Table 2, the magnetic disk of the present invention can improve the playback output by about 20% without reducing resolution, overwriting, and SRN characteristics. [Effects of the Invention] As described above, according to the method of manufacturing a magnetic disk according to the present invention, the magnetic anisotropy of the magnetic medium can be increased, and the reproduction output can be improved by about 20% compared to conventional products. becomes possible. In addition, since there is no need to perform media plating immediately after texturing, it is possible to allow more time to stand between texturing and media plating, and the magnetic properties can be maintained stably for a long period of time. can.

Figure 1 Second

[Brief explanation of the drawing]

Figure 1 is a flow sheet showing the manufacturing process of the present invention;
The figure is a flow sheet showing the manufacturing process of the conventional technology.
FIG. 3 shows a magnetic hysteresis curve measured for the magnetic disk of the present invention, and FIG. 4 shows a magnetic hysteresis curve for a conventional magnetic disk. Figure 5 is a graph showing the relationship between the leaving time after texturing and the magnetic properties. Figure 3 Figure 4 Procedural amendment (voluntary) 1. Case description: Patent Application No. 149985 of 2007 2. Name of the invention Method for manufacturing magnetic disks 3. Relationship with the case of the person making the amendment Patent applicant address 5-11-3 Shinbashi, Minato-ku, Tokyo Name
(227) Katsumi Uchida, Representative of Sumitomo Light Metal Industries, Ltd. 4. Agent 〒171 Figure 5 0 Dry storage (θ direction) ● Dry storage (r direction) 8 Storage in Ar (θ direction) ▲ Storage in Ar (r direction) Storage in water (θ direction) 1 Underwater storage (r direction ) (1) "Substrate surface roughness..." on page 4 of the specification, lines 12 to 13 is corrected to "base surface roughness..." (2) Page 5 of the specification, Correct "Organic abrasive grains, ..." from line 10 to line 11 to "free abrasive grains, ...". (3) "Substrate roughness..." on page 7, line 6 of the specification. ·"of"
Substrate roughness..." is corrected. Below

Claims (2)

[Claims] 1. An aluminum alloy disk or an aluminum alloy disk having a Ni-P plated surface was used as a base, the base surface was polished smooth and Ni-P plated, and then striations were formed in the circumferential direction by texturing processing. A method for manufacturing a magnetic disk, which comprises subsequently forming a magnetic recording layer. 2. 2. The method of manufacturing a magnetic disk according to claim 1, further comprising the step of drying or storing the textured substrate under an inert gas atmosphere.